Running a 2-cycle engine with the wrong gas/oil mixture can seriously damage your equipment, and running one without any oil in the fuel will completely destroy your tool's engine in minutes.
Many tool users have questions about oil/gas mixtures in 2-cycle engines, and many engines require different mixture ratios.
This article explains what tool owners need to know to properly mix oil into the fuel of their 2-cycle engine equipment. Mixing steps, engine mixture ratios, gasoline storage procedures, and damage prevention tips are explained below.
How Long Does Gasoline Keep?
Using "new" gasoline in a gas-powered engine isn't always the same as using fresh gasoline.
The gas you pour into your equipment's fuel tank might be "new" because it just came from the gas can, but how long has the gasoline in your can been sitting there?
Many tool owners are unaware that gasoline expires. The general rule of thumb is that gasoline can store for three to six months before becoming unhealthy for use in engines. After a few months, gasoline begins to break down and loses the full potency of its combustible properties. Using old gasoline will reduce the power output of your tool's engine, and it can also cause excessive build-up of impurities in an engine's parts. Here are some tips for proper gasoline storage and use:
- Discard gasoline after storing it for three to six months. Discarding any remaining gasoline in your garage or shed at the start of each season is a smart habit to develop.
- If you store your gas-powered equipment with fuel inside their gas tanks, use a fuel stabilizer to protect the carburetors of your tool engines.
- Even if you use a fuel stabilizer in your tool engines when you store them, discard the gasoline at the start of the next season. It's only there to keep your carburetor from drying up.
- If you're determined to store gasoline for long periods of time, use a fuel stabilizer. Many tool owners mix stabilizer in their fuel just as a general practice. Fuel stabilizer can extend the life of stored gasoline up to several more months.
2-Cycle Oil/Gas Mixture Ratios: Then and Now
Every 2-cycle engine has a specific gas/oil mixture ratio, so the first step in mixing your 2-cycle engine oil is determining the correct ratio for your tool's engine. Most 2-cycle tools display the correct gas/oil ratio somewhere on the tool, usually the engine housing. If not, the tool's owner manual will have the ratio information. If the tool's owner manual is misplaced, most manuals can be accessed on manufacturer websites. Measuring for 2.6 Ounces of 2-Stroke Oil
Almost every newer 2-cycle engine uses a 50/1 gas to oil ratio, as opposed to older tools that use more oil. This is because the lawn & garden industry is designing cleaner-running gas engines. Older gas-powered tools may use gas/oil ratios of either 40/1 or 32/1. Here's the catch: because the industry is shifting heavily towards 50/1 ratio 2-cycle engines, most of the 2-cycle engine oil products available on the market today are sized so that an entire bottle can be conveniently added to round gallon figures (like 1 gallon), producing a 50/1 mixture. For example, the 2-cycle engine oil products pictured below come in 2.6 oz. bottles. 2.6 ounces of oil is exactly the quantity needed to produce a 50/1 mixture with exactly 1 gallon of gasoline. Larger, 6.4 oz. 2-cycle oil bottles are also available for mixture with exactly 2 and 1/2 gallons of gasoline, again producing a 50/1 mixture.
Because the 2-cycle oil market favors container sizes geared toward 50/1 gas/oil mixtures, you will have to do some extra careful measuring if your 2-cycle engine accepts a 40/1 or 32/1 mixture. Most of the oil bottle sizes on the market are 2.6 ounces (for 1-gallon 50/1 mixtures). Because it is much easier to accurately measure larger volumes of gasoline (as opposed to small volumes of oil), we've expressed our measurements for 40/1 and 32/1 mixtures below so that tool owners can simply add an entire 2.6 oz. bottle of oil to a modified quantity of gasoline. Measuring out the gasoline is much easier than measuring out the oil. One last comment. The best case scenario is obviously a precise mixture measurement. That being said, it's always best to mix more oil than less oil if you're unsure.
50/1 Mixture Measurements:
2.6 ounces of 2-cycle oil / 1 gallon of gasoline
40/1 Mixture Measurements:
2.6 ounces of 2-cycle oil / 0.8 gallons (approx. 103 ounces) of gasoline
32/1 Mixture Measurements:
2.6 ounces of 2-cycle oil / 0.65 gallons (approx. 84 ounces) of gasoline
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2-Cycle Engine Oil Mixing Steps 2-cycle engine oil must be mixed with gasoline in a separate gas container in order for it to mix correctly. Never mix 2-cycle oil directly into the fuel tank of your tool's engine. Here are the steps:
1. The oil should always be added first.
Pour the correct, pre-measured amount of 2-cycle engine oil into a clean, appropriately-sized gasoline container.
2. Add the correct amount of gasoline to the oil.
3. Seal the gas container and gently swish it until the oil completely mixes. Do not shake the gas container. These steps are very simple, but it's still important to take care to perform them in the correct order. [Back to top] 2-Cycle Oil and Engine Damage Mixing too much oil in your 2-cycle engine is much less damaging to the engine than mixing too little oil. If there's only a little too much oil in the mixture, you may not notice any difference in your tool's performance at all. The important thing is that it's being lubricated. If a lot of extra oil is mixed in the fuel, there are some symptoms that might appear:
- smoky exhaust
- oil out the muffler
- loss of engine power
You'll know that it's happened almost immediately, because the engine will seize and become permanently unusable.
Mixing too little oil in you 2-cycle engine will similarly damage your tool's engine, but over a longer period of time.
Lack of engine power is the most prominent sign that a 2-cycle engine is running on too little oil. Permanent damage can be prevented if the problem is corrected early, but such an outcome would be very fortunate. This is why it is so important to mix your 2-cycle engine oil at the correct ratio for your tool. Using fresh fuel and the correct oil/gas mixture ratio prevents all of these potential problems. Watch this article's demonstration video to see what happens when a 2-cycle engine is run without oil in the fuel:
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eReplacementParts.com stocks parts for thousands of 2-cycle engines and other Small Engine Parts used in power tools and equipment of all kinds. Our website's breakdown schematics, how-to articles, and Repair Forum are here to give tool owners all the information tools they need to keep their engines running at a level of professional maintenance. [Back to top] What we're about.